This invention relates to an internal combustion engine equipped with a reactor for oxidation of the unburned constituents contained in the exhaust gases discharged from the combustion chambers of the engine, and a method of controlling the temperature within the reactor.
In connection with an internal combustion engine equipped with a reactor for thermally oxidizing the unburned constituents such as carbon monoxide and hydrocarbons contained in the exhaust gases discharged from the combustion chambers of the engine, it is known that the temperature in the reactor is maintained relatively high when the concentration of the unburned constituents in the exhaust gases increased, whereas the temperature is maintained relatively low when the concentration of the unburned constituents is decreased. It is also known that this unburned constituents concentration is increased as the air-fuel ratio of the air-fuel mixture supplied to the combustion chambers becomes lower.
Accordingly, the reactor requires to supply the engine with a richer air-fuel mixture having a lower air-fuel ratio. However, usual engine are supplied with an air-fuel mixture having an air-fuel ratio ranging from 12:1 to 13.5:1 in consideration of preventing the increase of the fuel consumption. Even engine operation on the air-fuel mixture having such a range of air-fuel ratio raises the temperature of the reactor as high as about 840.degree. to 980.degree. C. Additionally, even in the case in which the reactor temperature control is carried out, the reactor temperature is within the above-mentioned high temperature range.
However, experiments reveal that the unburned constituents in the exhaust gases can be sufficiently reacted or oxidized within the reactor even at a temperature lower than the above-mentioned high temperature range. In view of this fact, it is desirable to maintain the reactor temperature as low as possible within a temperature range in which sufficient oxidation reaction of the unburned constituents in the exhaust gases is accomplished.